Aircraft manufacturers are under an increasing pressure to produce light-weight, strong and resistant aircraft which also has the lowest productions costs and also low costs for maintenance during the entire lifetime of the aircraft. An aircraft must be strong enough to cope with stresses during take-off, high altitude cruising and landing, and at the same time it must be as easy as possible to maximise the performance of the aircraft. Partly because of this, aircraft manufacturers have started to use fibre reinforced resin matrix composites.
Such fibre reinforced resin matrix composites provide improved strength, wear resistance, rigidity and strength-weight relationship by comprising strong, rigid carbon fibres in a softer, more tensile resin matrix. The resin matrix material transmits forces to the fibres and provides stretching and toughness characteristics, since the fibres bear a major part of the applied forces.
Known methods for producing fibre reinforced resin matrix composites for an aircraft comprise that a number of so called prepreg sheets, or simply abbreviated as “prepregs” are put on top of each other in contact with a moulding tool. The prepreg consists of unidirectional fibres or multi-directional fibres in an uncured resin. A vacuum bag is placed over and is sealed towards the moulding tool so that the entire component is completely enclosed. Vacuum is then applied to the enclosed component so that the prepregs are becoming compacted towards the surface of the moulding tool. Finally the prepreg is cured, wherein the resin first assumes a low viscosity and fills out, subsequently the temperature is increased further and the resin cures. The temperature is then decreased and the object gets loose from the moulding tool. When producing e.g. a composite spar it is usually an advantage to have a female tool for obtaining good tolerances of the outer surfaces. It is often difficult to put the composite laminate down in the radii of the female tool, i.e. in inner corners, concave surfaces and similar. The composite laminate tends to hang up and form enclosures of air in the radii or corners having another shape than what is desired.